This week, through December 19, the special sale includes:
75% off Premium Wallet Upgrade 248 LP (regular price 995 LP)
35% off Universal Solvents (versus 20% off when included in weekly sale)
50% off Crafting boosts, including guaranteed crit
The Premium Wallet Upgrade is a must-have. It allows many tokens that are bound-to-character or bound-to-account to be stored in your wallet rather than using inventory or vault space. You only need to buy it once per account. It applies to all characters on all servers. The regular price 995 LP is high, it is rarely on sale, and the 75% discount is great.
Universal Solvents are needed to craft essences or to upgrade essences to higher tiers. Although they are regularly on sale for 20% off, this sale is 35% off. If you buy them in larger quantities, x5 or x25, the price is lower than if you buy them one at a time.
One of the crafting boosts that are on sale is the 100% Craft Crit, which guarantees the next item you make will crit. If you will be crafting the level-cap items that require 10 special drops, you may want to be sure the recipe will crit. They are half price, and if you buy the x5 or x10, the price per item is lower. Be careful when purchasing. You want the 100% Craft Crit, not the similarly named +100% Crafting XP.